In clinical departments, direct observations or procedures in a body cavity are performed in order to diagnose various disease states, see treatment effects, determine treatment policies, and the like. Conventionally, these operations have been performed with a very invasive approach such as exploratory laparotomy or exploratory thoracotomy. However, as endoscopic surgeries are recently becoming widely carried out, these are performed using an exploratory laparoscope or an exploratory thoracoscope in which the size of incisional wounds is smaller than that in conventional examples.
For example, Patent Documents 1 and 2 disclose trocar systems that, after being inserted into a body cavity by piercing the skin to form a hole having a small diameter, can easily increase the diameter of the through hole to provide a route for passing a surgical tool having a larger diameter. According to these systems, the size of an external wound of a patient is smaller and the recovery time is extremely shorter than those in conventional examples where a large incision according to the diameter of a surgical tool is made.
Meanwhile, a new minimally-invasive technique for suppressing an external wound of a patient to the extent possible is developed. This technique is known as Natural Orifice Translumenal Endoscopic Surgery (NOTES), and is a completely new technique that inserts a flexible endoscope from an orifice on the body surface (natural orifice: mouth, anus, vagina, etc.) of a lumen organ into the lumen, makes an incision or a perforation through the lumen organ wall to access a body cavity, and makes a diagnosis or performs procedures or treatment. Theoretically, this technique needs no incisional wound on the body surface (incisionless), and, thus, the invasiveness thereof is expected to be lower than that of an endoscopic surgery. In a foreign country, a successful clinical case of laparoscope-assisted transvaginal or transgastric “hybrid NOTES” is reported, and has been attracting great attention. In near future, non-laparoscope-assisted “pure NOTES” only with a flexible endoscope is expected to be introduced to clinical practice.
Various tools or apparatuses for use in such NOTES are developed (Patent Documents 3 and 4). For example, Patent Document 3 discloses a translumenal trocar tool, including an elongated flexible trocar sleeve and an elongated flexible obturator that is disposed through the trocar sleeve. It is described that, in this tool, a distal end portion of the obturator has means for facilitating tissue penetration of the distal end portion. However, this tissue penetrating means uses a blade as a cutting unit, and, when this tool is used, an incision is made through the lumen. Furthermore, also in an apparatus disclosed in Patent Document 4, a puncturing unit is configured to breach the wall of a body organ.
One of technical demands in such NOTES is to safely create a route for accessing a body cavity. In the case of a transgastric route as an example, it is necessary to minimize the risk of damaging adjacent organs to the extent possible when making an incision or a perforation through the stomach wall. Thus, “preliminary pneumoperitoneum method” is proposed that, before making an incision or a perforation through the stomach wall in NOTES, makes a puncture from the body surface into the peritoneal cavity using a pneumoperitoneum needle having a small diameter, and injects carbon dioxide in advance into the peritoneal cavity (Non-Patent Document 1). According to this approach, a space is formed between the stomach and adjacent organs, and, thus, the risk of damaging the adjacent organs when making an incision or a perforation through the stomach wall is significantly reduced. However, the operation of creating a preliminary pneumoperitoneum is a conventional blind puncture operation using a pneumoperitoneum needle, and, thus, this operation itself has a risk of inducing complications such as improper puncture of intraperitoneal organs.